Vertical axis sail bladed wind turbine

ABSTRACT

A vertical axis turbine is provided which comprises a plurality of flexible sail blades attached to a vertically extending, rotatable shaft by upper and lower blade attachment devices, and a power absorbing load device coupled to the rotatable shaft. The flexible sail blades are deployed and stabilized in operation by the centrifugal forces produced in response to rotation of the blades about the vertical axis of the shaft, whereby, in operation, aerodynamic forces acting on the sail blades can be transmitted to shaft without generating bending movements. The sail blades comprise plural elongate flexible sail panels, with flyweights being disposed between and secured to the ends of pairs of the sail panels. In different embodiments, passive flyweights, active flyweights (secondary turbines) and combinations of both types are used.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of my copending application,U.S. Ser. No. 07/289,247 filed on Dec. 23, 1988.

FIELD OF THE INVENTION

The present invention relates to vertical axis wind turbines and, moreparticularly, to improved wind turbines having sails for blades whereinthe blades are deployed and stabilized by the centrifugal forces actingon flyweights attached to the ends of the panels comprising the sails.

BACKGROUND OF THE INVENTION

Wind turbines are an ancient means of extracting the force, in the senseof being fuelless, energy of the wind. They have had a long andsuccessful history of contributing to such tasks as pumping water andmilling grain, tasks which could be done intermittently whenever thewind was available to do the work. With the pressure of competition fromthe internal combustion engine and its cheap power, the wind turbinewent into decline in that part of the world economy which either had oilor could afford to import it. By the time of the "oil crisis" of 1973wind turbines had been driven even from their historic role in thepumping of the Dutch polders.

With the disruptions of the oil supply in 1973, realizations arose thatfossil fuels would sooner or later become scarce and expensive. As theydid, the price of these fuels would rise and their quality, especiallytheir cleanliness, would fall. Furthermore, economies dependent uponimported fuels would be increasingly at the mercy of fewer and fewersuppliers. With these realizations many of the industrialized nationstried to find alternative sources of energy. The main result of theseprograms was to discover how difficult it was to find such sources whichcould compete economically with oil. Of the competing alternates, windenergy appears to have come closest to success. In addition to economicfactors, it has the further attributes of being free of chemicalpollution and the "greenhouse " effect.

The difficulty faced by existing wind-turbines is that their cost ofoperation, which is almost entirely the cost of the capital to buildthem, is too high. The principal reason for this difficulty is that theairloads are carried to the output through inefficient bendingstructures. In addition to the excessive cost and weight of theseprimary structures, several significant consequences flow from thisfundamental characteristic. Economies of large scale cannot be realizedbecause, after reaching some critical size, the cost of the rotatingcomponents of wind turbines increases with size at a ratedisproportionate to the value of the energy they produce. While this istrue for all turbine systems, it is doubly important in the wind energyarea because large scale turbines, by reaching higher into the availablewind, would capture much more energy from a given site therebyincreasing their role in the energy economy. A further obstacle to largesize wind-turbines has been the large torques they produce which must betransmitted through heavy and expensive drive components. To avoid theselarge torques, previous workers in the field have tried to mountsecondary turbines on the tips of the blades of their machines. Thesesecondary turbines would absorb the torque produced by the primaryturbine and convert it into mechanical energy at high rotational speedsand correspondingly low torques. These attempts have been unsuccessfulbecause of the structural systems required to support these tip turbineswere not cost effective.

Wind turbines would profit from the ability to operate at highrotational and tip speeds. This would have several favorable effects:such turbines would, in principle, have blades with narrower chords andhence weigh and cost less; and the higher rotational speed would producethe same power at lower torque lowering the cost and weight of thedriveshaft, couplings, gearbox and other components of the drive system.Conventional structural systems have, more or less, reached the pointwhere further increases in the tip speed would result, for reasons ofstrength, in such substantial increases in the blade thickness as tocause losses in aerodynamic efficiency outweighing any gains.

Conventional vertical axis wind-turbines have rigid blades and must,perforce, use essentially symmetrical airfoils thus losing theadvantages of the more efficient cambered airfoils. The blades ofpresent wind turbines require considerable tooling for economicmanufacture. As a result, it is prohibitively expensive to customizeblades and turbines to each users site. Turbine and blade designs arecompromised to average conditions and non-average installations sufferneedless performance losses. Turning to specific examples of the priorart, the leading example of state-of-the-art vertical axis wind turbinetechnology is the Darrieus turbine named for its inventor G. J. M.Darrieus, who applied for French patents on his machines in 1925 and1926 and for U.S. Pat. No. 1,835,018. A contemporary design of aDarrieus machine is described in the Sandia National Laboratories Report"Design and Fabrication of a Low Cost Darrieus Vertical Axis WindTurbine System, Phase II, Volume 2. Final Technical Report"SAND82-7113/2 and related documents. This form of machine, whichsimplified wind turbine design and construction considerably byeliminating yaw and pitch controls, became the paradigm of the verticalaxis wind turbine but is still too expensive to compete unaided againstoil. Blades formed into the shape of a "Troposkein" distinguish theDarrieus machine. This shape substantially eliminates the bendingmoments due to the inertial forces of the rotating blade and carriesthose loads in tension.

Important disadvantages of the Darrieus turbine include the fact that,since the turbine has curved blades, the blades are expensive tomanufacture and are not amenable to variable geometry. As a consequencethe Darrieus machine has no aerodynamic control and hence must bedesigned for unnecessarily high loads. In addition, the expense of theindividual blades requires turbines with few, usually two, blades thusprecluding the benefits which flow from the smoother operation ofseveral blades. Furthermore the Darrieus rotor is limited to symmetricairfoil sections and loses performance thereby in two ways: it is unableto profit from the superior aerodynamic efficiency of cambered airfoilsections and it is needlessly inefficient in the important neighborhoodof zero angle of attack.

The special "troposkein" shape of the rigid Darrieus blades eliminatesbending due to the centrifugal loads but leaves the weight and airloadsunaffected. Therefore, the blades of the Darrieus machine carry theprimary airloads in bending and these loads go through an alternation insign every revolution, a severe fatigue burden. Furthermore, as the sizeof the blades increases, the weight loads become a dominant and limitingfeature of these and all other rigid blade machines. Too, the rigidblade structure of the Darrieus machine is not amenable to carryingsecondary, tip turbines because of the large weight moments suchturbines would generate.

Vertical axis machines of the "Savonius" type, i.e. drag drivenmachines, have intrinsically low efficiencies which various workers havetried to improve. U.S. Pat. No. 4,359,311 (Benesh) teaches the use of anew, rigid bucket shape to improve the aerodynamic efficiency of hisSavonius-like machine . U.S. Pat. No. 4,496,283 (Kodric) provides amechanical means for varying the geometry of a Savonius machine. Asmentioned above and discussed below, the present invention involves theuse of sail blades and it is noted that the reference in the Kodricpatent to sailboats is gratuitous. U.S. Pat. No. 4,156,580 (Pohl)teaches another version of the Savonius machine with rigid blades. Noneof these teachings deal with actual sail blades.

Others have tried to provide control for lift-driven vertical axismachines. A leading example is U.S. Pat. No. 4,087,202 (Musgrove) which,for example, provides a straight, rigid bladed configuration withvariable geometry for control through a complex linkage which mustengender unnecessary aerodynamic losses in addition to added costs,maintenance and complexity. This line of attack has also been pursued inU.S. Pat. No. 4,105,363 (Loth) and in U.S. Pat. No. 4,334,823 (Sharp).

The word "sail" was formerly the generic name for what are now termedthe "blades". This nomenclature appears in many patent references whichshow rigid metal structures but refer to them as "sails". An example ofthis usage is contained in U.S. Pat. No. 4,245,958 (Ewers).

Some patents teach the use of semi-rigid blades. U.S. Pat. No. 4,355,956(Ringrose et al) teaches the use of a semi-rigid sail fastened along itsleading edge to a rigid spar. U.S. Pat. No. 4,561,826 (Taylor) teachesthe use of a blade which is elastically supple along its span. Neitherof these machines uses a flexible membrane which characterizes a truesail. A particular form of a semi-rigid sail is the "Princeton Sail"advocated by Sweeney and employed in U.S. Pat. No. 4,433,544 (Wells etal) and disclosed by Ahmadi in Wind Engineering Vol. 2, No. 2, 1978.This sail has a spanwise, rigid, leading edge member about which adouble membrane is wrapped. The trailing edge is supported by finecable. Ahmadi reports his maximum efficiency, i.e. power coefficient, tobe 0.008. This, about 1/50 of that of other machines, is too small to beof any use.

Heretofore, vertical axis wind turbines with sail-like blades have hadradial beams carrying spars or circular or polygonal frames from whichthe blades were supported. These configurations were used long ago inChina and Iran and one such turbine is in current use in Sweden to drivea carrousel in a children's park.

A photograph of an ancient Iranian turbine of this type is shown inAhmadi above. A very good example of a Chinese machine of this type isshown in Plate I of the well known book "Generation of Electricity byWind Power" by E. W. Golding. Such a machine is taught in U.S. Pat. No.4,052,134 (Rumsey) which shows sailboats with conventionally deployedsails sailing in an annular trough. U.S. Pat. No. 4,342,539 (Potter)shows square sails strung on booms with a telescoping mast. U.S. Pat.Nos. 4,545,729 (Storm) and 4,619,585 (Storm) teach the use of sailsmounted on a rotating frame with roller reefing gear to vary the amountof sail deployed and a deformable mechanism to provide variable camber.These constructions gain only a fraction of the advantages of structuralefficiency and variable geometry that sail blades can provide and thatonly at the expense of disadvantages in cost, weight and complexity ofthe rigid structures and mechanisms required to support them and theaerodynamic inefficiencies that they inevitably entail.

Most operators of wind-turbine installations would welcome systems whichare simple, efficient in their conversion of wind energy, inexpensive tobuild and operate, adaptable to their individual sites, capable ofcapturing the maximum amount of energy available at their sites, andavailable in sizes large enough to take full advantage of their sitesand are readily controllable.

SUMMARY OF THE INVENTION

In accordance with the invention, a variable geometry vertical axiswind-turbine is provided which uses structurally efficient sail bladesthat are deployed and stabilized without the usual lattice or sparsupports. From this basic structural system flow a broad range ofimportant economic advantages both in cost and in energy capture. Forexample, the efficient structure minimizes the loads to be borne by theblades thereby saving weight and cost. Further, the low cost bladestructure enables the economic use of a higher number of bladesresulting in a smoother running machine with lower ripple loads thusfurther increasing the structural efficiency and also reducing fatigueeffects. These low cost sail blades will be made of well developedmaterials and processes using a minimum of tooling and machinery.

By avoiding bending moments at the inception, the use of low solidityblading is made economic thereby increasing the operating tip speeds,reducing the torque loads throughout the drive system and reducing thegear ratio of the speed increaser.

The variable geometry of the turbine of the invention provides for thelimiting of load at high wind speeds thus providing for rating themachine at its economically optimum rating and avoiding wastefulover-rating of components as is the present practice.

Because of the intrinsically lighter and less expensive blade structureof the machine of the invention, the weight and cost growth with size isless rapid than with conventional turbines. Hence the most economic sizeof the turbine of the invention is increased substantially over that ofconventional turbines and greater gains in the economies of large scalecan be achieved.

Furthermore, the efficiency of the basic structure of the inventionprovides for the efficient carriage of secondary turbines. Thiscapability is a breakthrough in the size and economy of wind turbinessince very large turbines could be efficiently used without the largeincreases in torque loads and drive costs that would be encountered withconventional machines.

In addition to the above advantages in lower cost provided by theinvention, there are further advantages in energy capture. Specifically,the invention provides for blades which are automatically cambered toprovide higher aerodynamic efficiency thus increasing energy capture.The invention further provides for the variation of turbine capture areawith wind speed so that more energy can be extracted from the frequentlow wind speeds than conventional machines can without overloading themachine at high wind speeds. Because of the simple tooling required,blades can economically be tailor made for any specific wind site so asto extract the maximum amount of the available energy.

The invention also increases the market for wind turbines by makingviable low wind sites presently uneconomic.

Other features and advantages of the invention will be set forth in, orapparent from, the detailed description of preferred embodiments of theinvention which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one preferred embodiment of theinvention which includes three blades, three panels per blade and twopassive flyweights.

FIG. 2 is a fragmentary side elevation view of the embodiment shown inFIG. 1 taken in the direction 2--2.

FIG. 3 is a partial cross-sectional view taken approximately along line3--3 of FIG. 2.

FIG. 4 is detail of FIG. 2 showing one blade assembly.

FIG. 5 is a detail of FIG. 4 showing one panel assembly.

FIG. 6 is a cross-section of FIG. 5 taken in the direction of line 4--4.

FIG. 7 is a simplified cross-section of FIG. 2 in the direction of line5--5.

FIG. 8 is a front elevation of a second preferred embodiment.

FIG. 9 is a fragmentary side elevation of this second preferredembodiment.

FIG. 10 is a partial front elevation showing simplified details of thelower portion of the second preferred embodiment.

FIG. 11B is a partial front elevation showing simplified details of theupper portion of FIG. 8.

FIG. 11A is a partial section of FIG. 11 along line 6--6.

FIG. 12 is a sectional view of the active flyweight assembly along theline 7--7 of FIG. 8.

FIG. 13 is a front elevation view of the active flyweight assembly.

FIG. 14 is a rear elevation view of the active flyweight assembly.

FIG. 15B is a partial detail of FIG. 9 showing one blade assembly.

FIG. 15A is a sectional view of the lower blade panel taken along line8--8 in FIG. 15.

FIG. 16 is a schematic of a horizontal section of a sail rotor turbineas viewed from above, showing successive positions of a blade.

FIG. 17 is a schematic representation of an embodiment having threepanels per blade and incorporating both passive flyweights and activeflyweights.

FIG. 18 is a schematic representation of an embodiment having fourpanels per blade and incorporating both passive flyweights and activeflyweights.

FIG. 19 is a front-elevational view of a vertical axis turbine inaccordance with a third embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 show a first preferred embodiment of a vertical axis sailturbine, generally denoted 100, having three blade assemblies 200 eachof which has three panels and two passive flyweights 220. The winddirection is indicated by the broad arrow coming as substantially fromthe left. The turbine rotates in a clockwise direction when viewed fromabove.

Turning first to the speed increaser assembly, which is generallydenoted 140, the turbine 100 is set upon a base 120 which supports thespeed increaser assembly 140, the details of which are shown in FIG. 3.A drive shaft 162, which also serves as the turbine mast, is the inputshaft of the speed increaser 140 through a housing 143. A bull gear 144,attached to the housing 143, engages a pinion 145 which drives a highspeed shaft 146 and which is connected to an electric generator 150.This electric generator 150 also serves as the starting motor as will beexplained below. Mounted on a high speed shaft 146 is a brake disk 147cooperating with a brake caliper 148 which is mounted on the base 120. Astationary stub shaft 141 supports the housing 143 and hence the driveshaft 162 through a set of bearings 142a and 142b. The housing 143 alsosupports, for each of the blades, an idler shaft 182 and a hub reel 184disposed at appropriate positions along its periphery.

A drive assembly 160 is comprised of the drive shaft 162, which, asdiscussed above, is attached to the speed increaser 140 at its lower endand is supported at its upper end in an upper bearing assembly 164. Thelatter is positioned and supported by the set of guys 166. This methodof supporting the rotating shafts of vertical axis wind turbines is welladvanced. (See, for example, the Sandia documents referenced above.) Atthe top of the drive assembly is a lightning rod 168. At the properelevation along the drive shaft 162, as indicated by the phantom arrowin FIG. 1, there are attached three upper flyweight cradles 170U, onefor each blade appropriately disposed around the shaft perimeter.Similarly, at the appropriate elevation near the bottom of the shaftthere are three lower flyweight cradles 170L. Near the top of the shaft162, but beneath the upper bearing assembly 164, the fixed upper hub orblade attachment means, denoted 181, is fixed to the shaft 162.

Each of the blade assemblies 200, one of which is shown in some detailin FIGS. 4, 5 and 6, consists of three panels or panel assemblies, viz.,an upper panel 210U, a middle panel 210M and a lower panel 210L. Thephantom lines in FIG. 1 show the blade assemblies 200 in the furledposition 200F. The upper blade panels 210U ar attached to the driveshaft 162 by means of their end fittings through the fixed upper hub181. The lower ends of the upper blade panels 210U are attached to theupper flyweights 220U. The middle blade panels 210M are attached attheir upper end to their respective upper flyweights 220U and at theirlower end to their respective lower flyweights 220L. The lower bladepanels 210L are attached to their respective lower flyweights 220L attheir upper ends and are attached to their respective hub reels 184 attheir lower ends. To simplify reeling, the lower panels may be partiallyunclothed as indicated at U in FIG. 4.

A typical panel assembly, which is generally denoted 210, is shown inFIG. 5 and FIG. 6. Each panel consists of an appropriately shapedmembrane 212 made of woven or non-woven fabric, or a plastic film orother suitable material. The leading and trailing edges of the membrane212 are concave as shown. Attached to the leading edge of the membrane212 is a leading edge strength member 214 made up of flexible cable ofsuitable material such as a wire or fabric rope, or a parallel laidcable, terminating at both ends in a fitting, such as a clevis, suitablefor attaching this member to others as required. The leading edgestrength member 214 is enclosed in a suitably shaped aerodynamic fairing216, blunt at the leading edge and tapering smoothly into the membraneand is attached to the leading edge as shown. This fairing 216 iscomposed of a pliable material such as a natural or synthetic elastomer.A trailing edge strength member 218, which will generally beconsiderably smaller than the leading edge strength member, is attachedto the trailing edge of the membrane 212 and may be enclosed in suitabletrailing edge fairing 219. The leading and trailing edge members 214 and218 take on the concave shape of the membrane edges to which they havebeen attached. The passive flyweight 220 is made of any suitablematerial and shaped into a streamlined form as shown. Flyweight 220includes suitable mounting points so that the leading and trailing edgestrength members can be attached by means of their end fittings. Theflyweights 220 are positioned on the chord of the panel so that theircenters of gravity C.G. are located less than 25% the distance betweenthe leading and trailing edges aft of the leading edge attachment. Thecurvatures of the leading edges of the panels will be correspondinglyless than that of the trailing edges of the panels.

Referring to FIG. 7, which is a simplified cross-section of FIG. 2 takenin the direction 3--3, a control hub assembly 180 of the reel type isshown. In this embodiment, reels 184, one for each blade, areconveniently mounted on the housing 143 of the speed increaser 140. Eachreel 184 comprises a bracket 188 supporting a reel shaft 189 on whichare mounted grooved drums 185. A master reel 184M is motor driven by areel motor 187 and is connected to the other reels by synchronizingshafts 186 and universal joints 190 so that all blades are deployed andfurled in synchronism.

A second preferred embodiment of the invention is shown in FIG. 8 andFIG. 9. In this embodiment, the wind turbine, which is generally denoted300, has two blade assemblies 330 each having two panels and carrying anactive flyweight assembly 340 in place of the passive flyweights in theprevious embodiment. As will be evident from the description below, theuse of secondary turbines of the active flyweight assemblies 340eliminates the need for the mast to act as a drive shaft and replacesthe one large speed increaser with a small gearbox in each activeflyweight. As is also discussed below, the blade control of thisembodiment is a sliding hub which replaces the reel hub of the firstpreferred embodiment.

Turning first to the spindle assembly, which is generally denoted 320, abase 302 supports a stub shaft 304 which carries a bearing set (notshown) similar to that described above which supports a housing 308which is free to rotate about the stub shaft 304. A slip-ring assembly306 is mounted on the stub shaft 304. On the housing 308 there aremounted attachment ears 315 to which leading edge strength members 332and trailing edge strength members 334 of lower blade panels 331L areattached. The lower end of the spindle shaft 320S is mounted on therotable housing 308. At the appropriate positions on the shaft, onecradle 313 for each blade is attached to receive the active flyweightassemblies 340 in their retracted positions. The upper end of thespindle shaft 320S is supported in the upper bearing assembly 312 whichis stayed in position by three guys 366 spaced uniformly around theupper bearing assembly 312 much as in the previous embodiment describedabove. An antenna 311 is attached to the top of upper bearing 312.

Considering the sail blade assemblies 330, the upper panels 331U of theblades are attached ears 326 of to a sliding control hub 324 in a mannersimilar to that described above. The sliding control hub 324 has splinesockets to engage splines 322 on the spindle shaft 320S so as to permitsliding motion of the hub 324 along the spindle shaft 320S but toprevent rotation of said hub with respect to the spindle shaft 320S.Control cables 328 are attached to the sliding control hub 324. Thecontrol cables 328 run over pulleys 329, which are attached to the topof the hollow spindle shaft 320S, and then continue down into theinterior of spindle shaft 320S where these cables are attached to thedrum of a cable drive system. The art of reeling cables is welldeveloped and the cable reeling arrangement will not be describedfurther here.

Turning now to the active flyweight assemblies 340 which are shown inFIGS. 12, 13 and 14, the lower ends of upper blade panels 331U and theupper ends of lower blade panels 331L of each assembly are attached tospiders 342 of the active flyweight assembly 340 as shown in FIG. 13.Mounted on the spiders is a cowling 341. The secondary turbine 343 ofthe active flyweight assembly 340 is coupled to a gearbox 345 which actsas a speed increaser. The gearbox 345 is mounted on an aft spider 342A.The output shaft of the gearbox carries the disk of the brake 348 and iscoupled to a high speed generator shaft 347 through a coupling 346. Agenerator/motor 349 is mounted on a forward spider 342F. Methods formounting turbines, gearboxes and rotating loads in cowlings is wellknown in the aircraft propulsion field and will not be described furtherhere.

The configuration shown has the secondary turbine 343 aft of thegenerator 349. This arrangement simplifies the mechanical problem ofgetting the center of gravity of the active flyweight 340 at the desiredlocation, at the expense of some loss in aerodynamic efficiency. Inother embodiments the arrangements can be reversed to get betteraerodynamic efficiency and accept the mechanical difficulties needed toget the proper location of the center of gravity. Rotating electricaloutput cables 362, which rotate with the blades, are led through theforward spider arms 342F into leading edge fairings 333 of thecorresponding lower blade panels 331L and then down to the lower ends ofthe lower blade panels 331L where they leave the blade and are connectedto the input brushes of a slip ring assembly 306. Stationary outputcables 368 are connected to the output brushes of the slip ring assemblyand leave the turbine to be connected to the electrical load, as shownin FIG. 10. For Simplicity, the ground cable is not shown.

Referring to FIG. 15B, the two blade assemblies 330 are basically thesame as the previously described blade assemblies 200 except that theycomprise two panels, denoted 331U and 331L, per blade attached to oneactive flyweight 340, as shown in FIG. 15B. The leading edge fairing 333of the lower panel 331L contains the rotating electrical output cables362. The trailing edge fairing 335 contains the rotating electricalground cable 364.

A sliding control hub assembly, denoted 324, is best seen in FIGS. 11Band 11A. The sliding control hub 324 is engaged in sliding engagementwith the spindle shaft 320S by splines 322 and cooperating splinesockets in the hub. The terminations of the upper blade leading edgestrength members 332 and trailing edge strength members 334 areconnected to their corresponding ear attachments 326 which are integralwith the sliding hub 324. The control cables 328 are connected to thesliding control hub 324 and run over the control pulleys 329 and downinto the hollow drive shaft 320S and to a cable reel control system (notshown).

The two preferred embodiments discussed in detail above incorporateseveral elements which can be associated in a wide variety of otherembodiments to suit the needs of particular installations. For example,the reel hub described in connection with the first embodiment can beused in place of the sliding hub in an embodiment employing two bladesor active flyweights described in the second embodiment. Embodimentsusing three blade panels can have five blades rather than the threeshown. Further, FIG. 17 illustrates schematically a three paneledconfiguration having active flyweights with secondary turbines S as thelower flyweights and passive flyweights P for the upper flyweights. Suchan embodiment economizes the use of secondary turbines without foregoingthe large capture area of a three panel blade. FIG. 18 is an embodimenthaving four panels per blade where the upper and lower flyweights P arepassive and the central flyweight S is an active flyweight. Thisembodiment increases the capture area above that of the previousembodiment at some increase in complexity and cost. It will beappreciated that there are many other combinations of components whichcan be arranged into other embodiments as needed.

Considering the operation of the first preferred embodiment, when theturbine 100 is idle, the blades are in the furled position denoted bythe dashed lines 200F in FIG. 1, lying roughly parallel to the shaftwith the flyweights 220 in their cradles 170. When wind speeds aredetermined to be sufficient to start operations, remote electricalcontrols are used to energize the electric generator 150 and start itoperating as a motor turning the high speed shaft 146. The pinion 145mounted on the high speed shaft 146 turns the bull gear 144 with whichit is engaged. The drive shaft 162 is connected to the bull gear 144through the housing 143, and rotates with said bull gear 144. Theflyweights 220 which are in their cradles 170 rotate with the driveshaft 162. The centrifugal forces developed on the flyweights 220 as aresult of this rotation tense the leading and trailing edge strengthmembers 214 and 218 attached to them and tend to deploy the blades 200but are restrained by their reel hubs 184. The blades are deployed bycontrolled actuation of the hub control motor 187 which pays out theleading edge strength member 214 and the trailing edge strength member218 at the desired rate and in unison. At a certain point in theirdeployment, depending on the wind speed, the blades produce sufficienttorque to overcome the friction in the system and produce net power. Atthis point, the electric generator/motor 150 is driven by the turbineand operates as a generator. The blade deployment continues until theblades are deployed to the required diameter. The tensions in the panelleading edge strength members 214 and trailing edge strength members 218tend to straighten these members and thereby induce chordwise tensionsin the membrane 212. The combined effects of the tension field in themembrane and the centrifugal and aerodynamic pressures determine theshape the sail blades assume.

Under normal operation of the turbine, the sail blade changes camberwith its position relative to the wind as indicated in the schematicdiagram of a particular section in FIG. 16. At position A, the blade isin the upwind position and experiences a positive angle of attack. Theaerodynamic pressure, associated with that angle of attack, dominatesover the centrifugal pressure, contributed by the surface density of themembrane 212, and the sections are cambered inwardly toward the axis ofthe rotor. This camber provides more lift and better aerodynamicefficiency than an uncambered blade. As the blade rotates towardposition B, the aerodynamic pressure declines to zero. Here thecentrifugal pressure acting on the membrane tends to arch the sectioninto the curvature of its path around the axis. Moving toward theup-wind position, the angle of attack takes on negative values and theaerodynamic pressure combines with the centrifugal pressure to camberthe section outward away from the axis. This negative camber has thesame beneficial effect on the aerodynamic efficiency at negative anglesof attack as the positive camber had for positive angles. Moving from Cto D the angle of attack reduces to zero and the section membrane isarched into the circular path. Moving from D to A, the angle of attackonce again becomes positive and the section cambers inwardly.

As the wind speed changes, the control system changes the amount ofblade deployed to optimize the energy capture. If the wind speedincreases beyond that for which the system is designed, the blades canbe retracted to restrict power to the design load until such time as thewind moderates.

To retract the blades, the hub control motor 187 is actuated in thedirection to reel in the blade leading edge strength member 214 andtrailing edge strength member 218 and restore the flyweights to theircradles 170 along the course indicated by the dashed arrows of FIG. 1 byreversing the procedure for deployment. In the event of a failure of theload, such as may happen when the electrical connections between theoutput cables 152 and the network are broken, the turbine willaccelerate and tend to overspeed. To prevent overspeed from occurringthe brake 147/148 is engaged to replace the electrical load and theretraction procedure followed to stop the turbine.

Considering the operation of the second preferred embodiment, when theturbine 300 of this embodiment is idle, it is in the same state asdescribed above for the idle condition and the blades are in the furledstate indicated by the dashed lines 330F in FIG. 8. In this state, theupper control hub 324 will be in its highest position on the spindleshaft 320S. To start the turbine, the remote controls are used toenergize the generator/motor 349, but for this embodiment, the motordrives the secondary turbine 343 in the sense opposite to that in whichit rotates as a turbine. This reversed operation will cause thesecondary turbines to operate as propellers and they will produce thrusturging the active flyweight assemblies forward and carrying the primaryblade assemblies with them causing the spindle shaft 320S to rotate inits bearings. The centrifugal forces resulting from the rotation of theactive flyweight assemblies 340 will tense the leading and trailing edgestrength members 332 and 334 tending to deploy the blades, but theseblades will be restrained by the blade control cables 328. By actuatingthe cable control system, the sliding control hub 324 will be permittedto descend, in a controlled fashion, along the splines 322 on thespindle shaft 320S thus permitting the blades to deploy. As therotational speed of the primary turbine increases under the urging ofthe propeller action of the secondary turbines 343, energy from the windwill be captured and torque provided to further accelerate the blades,thereby reducing the thrust required of the propeller action of thesecondary turbine 343. As this acceleration takes place, the excitationof the generator/motor 349 will be modulated and the motor speed broughtto zero and then permitted to accelerate as power is extracted from thewind by the primary turbine blades.

As in the above embodiment, the overall control system will control theextent of deployment so as to capture the optimum amount of energy. Asthe wind speed increases above the rated wind speed, the control systemwill contract the rotor so as to avoid overloading the systemcomponents. In order to return the turbine to the idle or standby state,the blades are furled by raising the sliding control hub 324 undercontrol of the cable control system. As the primary turbine reaches thespeed at which it no longer produces torque, the secondary turbines canagain be engaged as propellers or as aerodynamic brakes by adjustingtheir rotational speeds and the direction of rotation in a procedureessentially the reverse of the starting procedure described above.

In the event of loss of load, there is the possibility of both theprimary and the secondary turbines overspeeding. Again brakes 348 areprovided to absorb the energy of the secondary turbines and to preventsuch overspeeding. The primary turbine will have no tendency tooverspeed if the secondary turbines are braked and the normal furlingprocedures as described above would be employed to stop the rotor. Asthe rotational speed decreases to the point where no energy is beingabsorbed by the primary turbine, the brakes can be gradually releasedand the secondary turbines used to control the final phase of furling.

A third preferred embodiment of the invention is shown in FIG. 19. Inthis embodiment, the wind-turbine, which is generally denoted as 400, isbroadly similar to the second embodiment described above in connectionwith FIG. 8, and other related figures, in that both embodiments employsecondary turbines to absorb the power of the primary turbine. Inparticular, the blade assembly of this embodiment, which is denoted 430,is similar to the blade assembly 330 of FIG. 15.

In the embodiment of FIG. 19, a base 402 supports a stationary,non-rotating mast or shaft 404. A lower hub 406 is positioned on themast 404 by a thrust bearing (not shown) which allows the lower hub 406to rotate freely about the mast 404. Hub reels 408 are supported by thelower hub 406. A circular cradle 410, capable of receiving activeflyweights 432 at all positions around the shaft, is attached to thestationary shaft 404. An upper hub 412 is positioned on the mast orshaft 404 by a thrust bearing (not shown) which allows hub 412 to rotatefreely. A slip-ring assembly 420 is attached to the shaft 404 above theupper hub 412. Rotating output cables 422 are attached to the inputbrushes of the slip-ring assembly 420 and stationary output cables 424are attached to the output brushes of the slip ring assembly 420 and ledthrough the hollow shaft 404 to the base where cables, which are denoted424a at the base, can there be connected to the load. Guy wires 442 areattached to the shaft 404 through attachment ring 440.

The operation of this third preferred embodiment of the invention is inall ways the same as the operation of the second preferred embodimentpreviously described.

It will be appreciated from the foregoing that the invention providesfor an extensive family of inexpensive and efficient wind turbines.

While the above description contains many specific details, these shouldnot be construed as limitations on the scope of the invention, butrather as exemplifications of preferred embodiments. Many othervariations are possible. For example, the above description of theinvention has been illustrated as applied to the generation ofelectricity. The invention can be applied other intermittent power uses,such as pumping water, compressing air, direct heating, electrolysis ofwater and the other uses of energy. In these alternative uses, a meansmust be available for starting the turbine, since the turbine is notself starting. Furthermore, although the description has been restrictedto vertical wind turbines, the invention could as well be applied totransverse turbines in other fluids such as water, oil, etc. Further,the invention has been described in connection with two and three bladedturbines. Machines with other numbers of blades are equally valid.Accordingly, the scope of the invention should be determined not by theexemplary embodiments illustrated but rather by the appended claims.

    __________________________________________________________________________    NUMERIC SORT             ALPHABETIC SORT                                      __________________________________________________________________________    FIRST PREFERRED EMBODIMENT 100                                                120                                                                              BASE                  BASE                  120                            140                                                                              SPEED INCREASER ASSEMBLY                                                                            BLADE ASSEMBLY        200                            141                                                                              STUB SHAFT            BRACKET               188                            142a                                                                             UPPER BEARING ASSEMBLY                                                                              BRAKE CALIPER         148                            142b                                                                             LOWER BEARING ASSEMBLY                                                                              BRAKE DISK            147                            143                                                                              HOUSING               BULL GEAR             144                            144                                                                              BULL GEAR             CONTROL HUB ASSEMBLY  180                            145                                                                              PINION                CRADLE                170                            146                                                                              HIGH SPEED SHAFT      DRIVE SHAFT           162                            147                                                                              BRAKE DISK            ELECTRICAL OUTPUT CABLE                                                                             152                            148                                                                              BRAKE CALIPER         FINS                  225                            150                                                                              GENERATOR/MOTOR       FIXED HUB             181                            152                                                                              ELECTRICAL OUTPUT CABLE                                                                             FLYWEIGHT             220                            162                                                                              DRIVE SHAFT           FURLED BLADE          200F                           164                                                                              UPPER BEARING SUPPORT GENERATOR/MOTOR       150                            166                                                                              GUY                   GROOVED DRUM          185                            170                                                                              CRADLE                GUIDE ROLLER          182                            180                                                                              CONTROL HUB ASSEMBLY  GUY                   166                            181                                                                              FIXED HUB             HIGH SPEED SHAFT      146                            182                                                                              GUIDE ROLLER          HOUSING               143                            184                                                                              HUB REEL              HUB REEL              184                            185                                                                              GROOVED DRUM          LEADING EDGE FAIRING  216                            186                                                                              SYNCHRONIZING SHAFT   LEADING EDGE STRENGTH MEMBER                                                                        214                            187                                                                              REEL MOTOR            LOWER BEARING ASSEMBLY                                                                              142b                           188                                                                              BRACKET               MEMBRANE              212                            189                                                                              SHAFT                 PANEL ASSEMBLY        210                            190                                                                              UNIVERSAL JOINT       PINION                145                            200                                                                              BLADE ASSEMBLY        REEL MOTOR            187                            200F                                                                             FURLED BLADE          SHAFT                 189                            210                                                                              PANEL ASSEMBLY        SPEED INCREASER ASSEMBLY                                                                            140                            212                                                                              MEMBRANE              STUB SHAFT            141                            214                                                                              LEADING EDGE STRENGTH MEMBER                                                                        SYNCHRONIZING SHAFT   186                            216                                                                              LEADING EDGE FAIRING  TRAILING EDGE FAIRING 219                            218                                                                              TRAILING EDGE STRENGTH MEMBER                                                                       TRAILING EDGE STRENGTH MEMBER                                                                       218                            219                                                                              TRAILING EDGE FAIRING UNCLOTHED             U                              220                                                                              FLYWEIGHT             UNIVERSAL JOINT       190                            225                                                                              FINS                  UPPER BEARING ASSEMBLY                                                                              142a                           U  UNCLOTHED             UPPER BEARING SUPPORT 164                            SECOND PREFERRED EMBODIMENT 300                                               302                                                                              ANTENNA               ACTIVE FLYWEIGHT ASSEMBLY                                                                           340                            304                                                                              UPPER BEARING SUPPORT AERODYNAMIC FAIRING   350                            306                                                                              GUYS                  AFT SPIDER            342A                           308                                                                              FLYWEIGHT CRADLE      AFTERBODY             351                            310                                                                              LOWER SUPPORT ASSEMBLY                                                                              ANTENNA               302                            311                                                                              BASE                  BASE                  311                            312                                                                              STUB SHAFT            BLADE ASSEMBLY        330                            313                                                                              HOUSING               BLADE ATTACHMENT EARS 315                            315                                                                              BLADE ATTACHMENT EARS BRAKE                 348                            320                                                                              SPINDLE SHAFT         CONTROL CABLE         328                            322                                                                              SHAFT SPLINE          COWLING               341                            324                                                                              SLIDING HUB           ELECTRICAL GENERATOR/MOTOR                                                                          349                            324F                                                                             SLIDING HUB AT FURL POSITION                                                                        FLYWEIGHT CRADLE      308                            326                                                                              UPPER ATTACHMENT EARS FOREWARD SPIDER       342F                           328                                                                              CONTROL CABLE         FURLED BLADE ASSEMBLY 338F                           329                                                                              PULLEY                GEARBOX (SPEED INCREASER)                                                                           345                            330                                                                              BLADE ASSEMBLY        GUYS                  306                            330F                                                                             FURLED BLADE ASSEMBLY HIGH SPEED COUPLING   346                            331L                                                                             LOWER SAIL PANEL      HIGH SPEED SHAFT      347                            331U                                                                             UPPER SAIL PANEL      HOUSING               313                            332                                                                              LEADING EDGE STRENGTH MEMBER                                                                        LEADING EDGE FAIRING  333                            333                                                                              LEADING EDGE FAIRING  LEADING EDGE STRENGTH MEMBER                                                                        332                            334                                                                              TRAILING EDGE STRENGTH MEMBER                                                                       LOWER SAIL PANEL      331L                           335                                                                              TRAILING EDGE FAIRING LOWER SUPPORT ASSEMBLY                                                                              310                            336                                                                              SAIL MEMBRANE         PULLEY                329                            340                                                                              ACTIVE FLYWEIGHT ASSEMBLY                                                                           ROTATING ELECT. GROUND CABLE                                                                        364                            341                                                                              COWLING               ROTATING ELECT. OUTPUT CABLE                                                                        362                            342A                                                                             AFT SPIDER            SAIL MEMBRANE         336                            342F                                                                             FOREWARD SPIDER       SECONDARY TURBINE     343                            343                                                                              SECONDARY TURBINE     SHAFT SPLINE          322                            345                                                                              GEARBOX (SPEED INCREASER)                                                                           SLIDING HUB           324                            346                                                                              HIGH SPEED COUPLING   SLIDING HUB AT FURL POSITION                                                                        324F                           347                                                                              HIGH SPEED SHAFT      SLIP RING ASSEMBLY    366                            348                                                                              BRAKE                 SLIP RING ASSEMBLY    366                            349                                                                              ELECTRICAL GENERATOR/MOTOR                                                                          SPINDLE SHAFT         320                            350                                                                              AERODYNAMIC FAIRING   STATIONARY ELE. OUTPUT CABLE                                                                        368                            351                                                                              AFTERBODY             STUB SHAFT            312                            362                                                                              ROTATING ELECT. OUTPUT CABLE                                                                        TRAILING EDGE FAIRING 335                            364                                                                              ROTATING ELECT. GROUND CABLE                                                                        TRAILING EDGE STRENGTH MEMBER                                                                       334                            366                                                                              SLIPRING ASSEMBLY     UPPER ATTACHMENT EARS 326                            366                                                                              SLIP RING ASSEMBLY    UPPER BEARING SUPPORT 304                            368                                                                              STATIONARY ELE. OUTPUT CABLE                                                                        UPPER MAST ASSEMBLY   370                            370                                                                              UPPER MAST ASSEMBLY   UPPER SAIL PANEL      331U                           __________________________________________________________________________

What is claimed is:
 1. In a vertical axis turbine comprising a vertically extending, rotatable shaft; upper and lower blade attachment means for attaching at least one blade to said shaft, and a power absorbing load device coupled to said shaft; the improvement wherein said at least one blade comprises a flexible sail blade, made of fabric or film so as to have no substantial resistance to bending and thus to be limp under no load, and so that in operation, said blade cambers inwardly towards the axis of rotation of the shaft when the blade is in an upwind position and cambers outwardly away from said axis of rotation when the blade is in a downwind position, and attached at the ends thereof to said shaft by said upper and lower blade attachment means and deployed and stabilized in operation by the centrifugal forces produced in response to rotation of said blades about the vertical axis of said shaft, whereby, in operation, aerodynamic forces acting on said sail blades can be transmitted to shaft without generating bending moments, said blade having at least one flyweight secured thereto.
 2. A vertical axis turbine as claimed in claim 1 wherein said at least one sail blade comprises at least two flexible elongate sail panels arranged in end to end relation, said at least one flyweight being disposed between and secured to adjacent ends of said two sail panels.
 3. A vertical axis turbine as claimed in claim 2 wherein said at least one sail blade comprises a first sail panel connected at one end thereof to said lower attachment means and at the other end thereof to a second said flyweight, and a third panel connected at one end thereof to the first flyweight and at the other end thereof to a second said flyweight, and a third panel connected at one end thereof to the second flyweight and at the other end thereof to said upper attachment means.
 4. A vertical axis turbine as claimed in claim 2 wherein said flyweights comprise passive weights.
 5. A vertical axis turbine as claimed in claim 1 wherein one of said upper or lower blade attachment means comprises an attachment member mounted on said vertical shaft for movement therealong and means for providing movement of said attachment member along the shaft from a first position wherein the sail blade is furled and at least one further position wherein the sail blades is at least partially deployed.
 6. A vertical axis turbine as claimed in claim 5 wherein said attachment member comprises an attachment hub mounted in surrounding relation to said shaft and including sockets which engage in corresponding splines in said shaft.
 7. A vertical axis turbine as claimed in claim 1 wherein said at least one blade includes a leading edge and a trailing edge, said at least one blade comprising a leading edge strength member extending along and secured to the leading edge of the blade and a trailing edge strength member extending along and secured to the trailing edge of the blade.
 8. A fluid activated turbine for extracting energy from a fluid acting thereon, said turbine comprising:a shaft; a plurality of flexible said blades supported by said shaft and rotatable about an axis of rotation in response to fluid acting thereon, each sail blade being fabricated of a fabric or film having no substantial resistance to bending so as to be limp under no load, and such that, in operation, said sail blade cambers inwardly towards said axis of rotation when the blade is in a rotational position towards the direction of the fluid force acting thereon and cambers outwardly away from said axis of rotation when the blade is in a rotational position away from the direction of the fluid force acting thereon and including at least one flyweight secured thereto intermediate the ends of said blade; and energy extracting means responsive to rotation of said sail blades for extracting energy from action of said fluid.
 9. A fluid activated turbine as claimed in claim 8 wherein said shaft is stationary, wherein said turbine further comprises means for mounting said blades on said shaft for rotation about said shaft, and wherein said energy extracting means is incorporated in said flyweight.
 10. A fluid activated turbine as claimed in claim 8 wherein said shaft is rotatable, wherein said turbine further comprises means for mounting said blades on said shaft for rotation therewith, and wherein said energy extracting means is responsive to rotation of said shaft.
 11. A fluid activated turbine as claimed in claim 8 wherein said flexible sail blades each comprise at least two flexible elongate sail panels arranged in end to end relationship and said flyweight is disposed between and secured to adjacent ends of said sail panels.
 12. A fluid actuated turbine as claimed in claim 8, wherein each of said blades includes a leading edge and a trailing edge and each of said blades comprises a leading edge strength member extending along and secured to the leading edge of the blade and a trailing edge strength member extending along and secured tot he trailing edge of the blade.
 13. In a vertical axis turbine comprising a vertically extending, rotatable shaft; upper and lower blade attachment means for attaching at least one blade to said shaft, and a power absorbing load device coupled to said shaft; the improvement wherein said at least one blade comprises a flexible sail blase, made of fabric or film so as to have no substantial resistance to bending and thus to be limp under no load, said blade being attached at the ends thereof to said shaft by said upper and lower blade attachment means and being deployed and stabilized in operation by the centrifugal forces produced in response to rotation of said blades about the vertical axis of said shaft, whereby, in operation, aerodynamic forces acting on said sail blades can be transmitted to shaft without generating bending moments and the shape of the sail blades in profile is determined by the aerodynamic and centrifugal forces acting thereon, said blade having at least one flyweight secured thereto. 